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coords.py
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coords.py
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"""Coordinate sequence utilities
"""
from array import array
from ctypes import byref, c_double, c_uint
import sys
from shapely.geos import lgeos
from shapely.topology import Validating
try:
import numpy
has_numpy = True
except ImportError:
has_numpy = False
def required(ob):
"""Return an object that meets Shapely requirements for self-owned
C-continguous data, copying if necessary, or just return the original
object."""
if has_numpy and hasattr(ob, '__array_interface__'):
return numpy.require(ob, numpy.float64, ["C", "OWNDATA"])
else:
return ob
class CoordinateSequence(object):
"""
Iterative access to coordinate tuples from the parent geometry's coordinate
sequence.
Example:
>>> from shapely.wkt import loads
>>> g = loads('POINT (0.0 0.0)')
>>> list(g.coords)
[(0.0, 0.0)]
"""
# Attributes
# ----------
# _cseq : c_void_p
# Ctypes pointer to GEOS coordinate sequence
# _ndim : int
# Number of dimensions (2 or 3, generally)
# __p__ : object
# Parent (Shapely) geometry
_cseq = None
_ndim = None
__p__ = None
def __init__(self, parent):
self.__p__ = parent
def _update(self):
self._ndim = self.__p__._ndim
self._cseq = lgeos.GEOSGeom_getCoordSeq(self.__p__._geom)
def __len__(self):
self._update()
cs_len = c_uint(0)
lgeos.GEOSCoordSeq_getSize(self._cseq, byref(cs_len))
return cs_len.value
def __iter__(self):
self._update()
dx = c_double()
dy = c_double()
dz = c_double()
has_z = self._ndim == 3
for i in xrange(self.__len__()):
lgeos.GEOSCoordSeq_getX(self._cseq, i, byref(dx))
lgeos.GEOSCoordSeq_getY(self._cseq, i, byref(dy))
if has_z:
lgeos.GEOSCoordSeq_getZ(self._cseq, i, byref(dz))
yield (dx.value, dy.value, dz.value)
else:
yield (dx.value, dy.value)
def __getitem__(self, key):
self._update()
dx = c_double()
dy = c_double()
dz = c_double()
m = self.__len__()
has_z = self._ndim == 3
if isinstance(key, int):
if key + m < 0 or key >= m:
raise IndexError("index out of range")
if key < 0:
i = m + key
else:
i = key
lgeos.GEOSCoordSeq_getX(self._cseq, i, byref(dx))
lgeos.GEOSCoordSeq_getY(self._cseq, i, byref(dy))
if has_z:
lgeos.GEOSCoordSeq_getZ(self._cseq, i, byref(dz))
return (dx.value, dy.value, dz.value)
else:
return (dx.value, dy.value)
elif isinstance(key, slice):
res = []
start, stop, stride = key.indices(m)
for i in xrange(start, stop, stride):
lgeos.GEOSCoordSeq_getX(self._cseq, i, byref(dx))
lgeos.GEOSCoordSeq_getY(self._cseq, i, byref(dy))
if has_z:
lgeos.GEOSCoordSeq_getZ(self._cseq, i, byref(dz))
res.append((dx.value, dy.value, dz.value))
else:
res.append((dx.value, dy.value))
return res
else:
raise TypeError("key must be an index or slice")
@property
def ctypes(self):
self._update()
has_z = self._ndim == 3
n = self._ndim
m = self.__len__()
array_type = c_double * (m * n)
data = array_type()
temp = c_double()
for i in xrange(m):
lgeos.GEOSCoordSeq_getX(self._cseq, i, byref(temp))
data[n*i] = temp.value
lgeos.GEOSCoordSeq_getY(self._cseq, i, byref(temp))
data[n*i+1] = temp.value
if has_z:
lgeos.GEOSCoordSeq_getZ(self._cseq, i, byref(temp))
data[n*i+2] = temp.value
return data
def array_interface(self):
"""Provide the Numpy array protocol."""
if sys.byteorder == 'little':
typestr = '<f8'
elif sys.byteorder == 'big':
typestr = '>f8'
else:
raise ValueError(
"Unsupported byteorder: neither little nor big-endian")
ai = {
'version': 3,
'typestr': typestr,
'data': self.ctypes,
}
ai.update({'shape': (len(self), self._ndim)})
return ai
__array_interface__ = property(array_interface)
@property
def xy(self):
"""X and Y arrays"""
self._update()
m = self.__len__()
x = array('d')
y = array('d')
temp = c_double()
for i in xrange(m):
lgeos.GEOSCoordSeq_getX(self._cseq, i, byref(temp))
x.append(temp.value)
lgeos.GEOSCoordSeq_getY(self._cseq, i, byref(temp))
y.append(temp.value)
return x, y
class BoundsOp(Validating):
def __init__(self, *args):
pass
def __call__(self, this):
self._validate(this)
env = this.envelope
if env.geom_type == 'Point':
return env.bounds
cs = lgeos.GEOSGeom_getCoordSeq(env.exterior._geom)
cs_len = c_uint(0)
lgeos.GEOSCoordSeq_getSize(cs, byref(cs_len))
minx = 1.e+20
maxx = -1e+20
miny = 1.e+20
maxy = -1e+20
temp = c_double()
for i in xrange(cs_len.value):
lgeos.GEOSCoordSeq_getX(cs, i, byref(temp))
x = temp.value
if x < minx: minx = x
if x > maxx: maxx = x
lgeos.GEOSCoordSeq_getY(cs, i, byref(temp))
y = temp.value
if y < miny: miny = y
if y > maxy: maxy = y
return (minx, miny, maxx, maxy)